Terpenes induction

Terpene Induction of mldgut microsomal cytochrome P-450 and pyrethrum-dependent NADPH oxidation In southern armyworm larvae (42)... 

A recent example demonstrates that corals rely on induced biosynthesis of terpenes as a dynamic defense strategy as well. The induction of terpenoid secondary metabolites was observed in the sea whip Pseudopterogorgia elisabethae [162]. Levels of pseudopterosins 89-92, a group of diterpene glycosides with anti-inflammatory and analgesic properties (Scheme 23) [163-165], are increased in response predation by the mollusk Cyphoma gibbosum. First bioassays indicate that these natural products are involved in the chemical defense. 

These achiral poly(A -propargylamides) form helices with an equivalent amount of right- and left-handed screw senses. Addition of chiral alcohols induces predominantly one-handed screw sense in polyl7a and polyl7d. NMR spectroscopic analysis has revealed that the amide side chains interact with optically active alcohols by hydrogen bonding. Terpenes also induce a one-handed helix. In this case, hydrophobic interaction plays an important role for helix induction. 

Mur 207), has received renewed interest in recent years. A fine review covering the intermolecular asymmetric Diels-Alder reaction was compiled by Mori 208>. In this article the use of terpenes and carbohydrates as chiral auxiliaries is discussed no amino acid derivatives are mentioned in this context. A chiral a-hydroxycarboxylic acid derivative was also used to achieve an asymmetric Diels-Alder reaction 209). High asymmetric induction could be detected in the intramolecular Diels-Alder reaction of chiral molecules. 

Terpenes are found primarily in higher plants, less commonly in animals. They are often isolated by steam distillation or extraction. The major commercial applications of terpenes are as fragrance and flavoring agents. Terpenes often serve in organic chemistry as versatile carriers of chiral information. For example, (-)-a-pinene (2) is commonly used as a ligand for chiral induction. 

Double asymmetric induction with terpenes as chiral ene components Terada, M. Sayo, N. Mikami. K. Synlett 1995, 411. 

A wide variety of tandem, triple [12], and even quadruple [13, 14] cyclizations can be performed with multiply unsaturated 1,3-dicarbonyl compounds as shown in Eq. (1) [14] this provide intermediates for steroid and terpene syntheses. High levels of asymmetric induction can be achieved with phenylmenthyl acetoacetate... 

In order to carry out asymmetric cycloadditions of nitrosoalkenes, Reissig et al. have introduced chiral enol ethers derived from terpenes [378] and from the glucose derivative 4-46 [379]. Using these compounds, considerable asymmetric induction has been obtained thus, the 5,6-dihydro-4H-l,2-oxazine 4-45 was formed by hetero Diels-Alder reaction of 4-34 with chiral 4-44 in good diastereo-selectivity (Fig. 4-10) [379]. 

With chiral ketones, asymmetric induction takes place at a silicon center even with an achiral catalyst such as Rh(PPh3)3Cl, which is an application of the stereoselective hydrosiiyiation of cyclic terpene ketones (see 14.4.4.2). Double asymmetric induction is also effective and achieves a high optical yield ... 

Despite the thousands of secondary metabolites made by microorganisms, they are synthesized from only a few key precursors in pathways that comprise a relatively small number of reactions and which branch off from primary metabolism at a limited number of points. Acetyl-CoA and propionyl-CoA are the most important precursors in secondary metabolism, leading to polyketides, terpenes, steroids, and metabolites derived from fatty acids. Other secondary metabolites are derived from intermediates of the shikimic acid pathway, the tricarboxylic acid cycle, and from amino acids. The regulation of the biosynthesis of secondary metabolites is similar to that of the primary processes, involving induction, feedback regulation, and catabolite repression [6]. 

According to the proposed catalytic cycle for the asymmetric hydrosilylation of prochiral ketones1358,147, the a-siloxyalkylrhodium complex plays a key role for the asymmetric induction. The intermediacy of such species is strongly suggested in the hydrosilylation of cyclic terpene ketones catalyzed by RhCl(PPh3)3123, and further supported by spin trapping experiments in which spin adducts such as 24 are detected148,149,128. 

In this review, we examine the induced chemical defenses of P. abies, defenses whose levels increase following herbivore or pathogen attack. Induced defenses have attracted much attention in recent years because of their widespread occurrence in plants and their usefulness as subjects for study. Here, we cover the induction of several different classes of induced defenses in P. abies, including terpene-containing resins, phenolic compounds, and chitinases. Our focus is not only on their defensive roles, but also on how the levels of these compounds may be manipulated by biochemical and molecular methods while minimizing other phenotypic changes. Manipulation of defense compoimds in intact plants is a valuable approach to assessing their value to the plant. 

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